In the study of the branched-chain amino acids, the initial step in the catabolism of leucine is catalyzed by leucine 2,3-aminomutase. The product, Beta-leucine, is deaminated and cleaved to give acetate and isobutyrate. Leucine 2,3-aminomutase is dependent upon coenzyme B12 and is stimulated by FAD, coenzyme A, DPN, and pyridoxal phosphate. The enzyme is found, in addition to in bacteria and mammals, in bean seedlings, ryegrass, spinach, and potato tubers. BIBLIOGRAPHIC REFERENCES: Poston, J.M.: Leucine 2,3-aminomutase: A colbalamin-dependent enzyme present in bean seedlings. Science, 195, No. 4275, 301-302, 1977.